Silencer with cloth gas-conducting conduit



Get. 18, 1949. R. L.. LEADBETTER 2,485,392

SILENCER WITH CLOTH CTAS CNDUG'I'INGIA CONDUIT Filed Dec. 1s, 1944 l 2sheets-sheet 1 Oct, 18, 1949.

LEADBETTER SILENCER WITH CLOTH GAS-CONDUCTING CONDUIT 2 Sheets-Sheet 2Filed Dec. 13, 1944 INVENTOR. xO/Eooag @er Patented Oct. 18, 1949SILENCER WITH CLOTH GAS-CONDUCTING CONDUIT Ralph L. Leadbetter, Roselle,Ill., assignor to Burgess-Manning Company, Chicago, Ill., a corporationof Illinois Application December 13, 1944, Serial No. 568,035

9 Claims.

This invention relates to muiliers or silencers for smoothing the flowof pulsating gases to thereby prevent noise which would otherwiseresult.

The object of the invention is to provide an extremely simple, yeteffective, device for quieting such potential sources of noise as theintakes of internal combustion engines, intakes and discharges of aircompressors, and the like.

In carrying out the invention the pulsating gases are conducted througha tube or channel whose Walls are pervious to gases and includes afabric layer, as hereinafter more fully described, whose impedance tothe flow of gases through the material is such that the noise-provokingpressure fluctuations are effectively damped. In

certain embodiments of the invention, the influence of the pores of thefabric in smoothing the ow of gases in the main conducting channel issupplemented by limited sympathetic dilation and contraction of the tubeor channel itself.

Fig. 1 is a longitudinal sectional view of a silencer embodying theinvention;

Fig. 2 is a longitudinal sectional View of a silencer embodying adifferent form of the invention; and

Fig. 3 is a longitudinal sectional view of a silencer illustratinganother modified form of the invention.

Fig. 4 is a fragmentary view enlarged of a portion of the silencer ofFig. 2.

The simplest form of the invention is illustrated in Fig. l. Thissilencer consists essentially of casing l including end flanges 2, inletand outlet snouts 3 and 4, respectively, for connecting the silencerinto the line carrying the flowing gases, and a fabric tube 5 extendingthroughout the length of the device between the inlet and outlet snouts.The ends of this fabric tube are clamped around the internal ends of thesnout members by suitable means, such as steel tapes 6.

The diameter of casing l is preferably from two to three times that oftube 5, thus providing a space 'l of considerable volume in which thegases may expand or contract depending upon the flow through the fabricof tube 5 from or into the main conducting channel formed by the fabrictube.

In making tube 5, any suitable fabric produced from fibrous material andwhich is pervious to the iicw of air therethrough may be used. As usedherein, the term textile fabric means and is limited to cloth or othermaterial that is woven or knit from Vegetable, animal, or organic orinorganic synthetic fibers. Examples of suitable materials include ducl,burlap, and cloth woven from asbestos, glass, plastic, or other kinds ofber. Solid sheet materials rendered pervious by perforation are notsatisfactory and are not included as a permissible variant herein. Asingle layer of fabric is suflicient. For some applications it isdesirable to employ a double layer for strength but the eilciency of thesilencer is not necessarily thereby improved. Also, since the operationof the device depends upon the impedance of a single layer of the fabricas a multiple throttling valve, the device is in no way dependent uponthe absorption of sound energy by means of a sound absorbing body andmaterials generally and properly so classified are not used in thesilencing units of the invention herein described and claimed. In otherwords, the fabric employed in the silencer is pervious to, rather thanabsorptive of, sound.

The silencer of this invention may be employed in the quieting of gasespulsating in a conduit from a wide range of sources. The particularfabric to be used in any instance will depend upon the severity of thepressure fluctuations and the temperature of the gases since thematerial must be strong enough to resist rupture and must notdisintegrate when exposed to the temperature of the gases. Forconvenience, the conditions existent within the intake line of aninternal combustion engine may be used to illustrate the operation ofthe silencer. The sucking of the air into the engine cylinder as theintake valve opens results in a partia1 vacuum in the conduit at thevalve end and inward flow of the gases. When the intake valve is againclosed, the momentum of the moving gases in the conduit causes thebuilding up of a substantial pressure at the valve which propagates as apressure wave front outwardly Within the conduit. The timed recurrenceof this cycle results in more or less violent pulsating flow of the air,the amplitude of the pulsations depending upon many factors not heredescribed.

Propagation of the pressure wave within the intake line withoutsubstantial loss of amplitude results from the rigid confinement by thewalls of the pipe or conduit. The damping action of the silencer hereindescribed appears to be attributable to the partial liberation of thegases from such rigid confinement provided by the fabric tube as asegment of the conduit. The pressure of the wave fronts is substantiallydissipated as the gases flow through the pores or apertures of thefabric into the space "l, the direction of flow being reversed as thepressure front passes. The mpdance characteristics of the perviousfabric are such that effective smoothing of the flow of gases isobtained.

In addition to the materials listed above for use in the fabrication oftube 5, knitted fabrics may be employed. Fabrics of this type arelaterally stretchable so that the tube walls them selves may dilateunder the influence of the wave fronts permitting limited expansion ofthe gases Within the tube in addition to dissipation through its walls.Bias-cut woven fabrics function similarly but to a lesser extent. Theaction further serves to smooth the flow of gases.

A muling section of known construction is combined with a sectionembodying the invention in the silencer illustrated in Fig. 2. This unitis suitable for use as an intake silencer` for a Diesel engine. Theinterior of the unit within casing 8 and end anges 9 and I0 is dividedby a partitioning flange I I into two silencing sections. The firstsection through which the air passes in flowing from the atmosphere tothe engine comprises a perforated tube I2 extending through centralopenings in flanges 9 and II which tube is covered substantiallythroughout its length by burlap indicated at I3. Suitable means areprovided at the inlet end of this tube for connection of the silencerwith the intake piping. second section of the silencer of Fig. 2consists principally of a chamber I4 formed by baffle member I5 throughwhich perforated tubes I@ extend to conduct the gases to the zoneadjacent the silencer outlet IT.

The rst section of this silencer differs from the device of Fig. lprincipally in that the fabric impedance member is supported by aperforated metal tube I2 whereas the corresponding member 5 of Fig. 1 isunsupported. Hardware cloth or screening or other apertured materialsmay be used for supporting the fabric layer I3. In the particularembodiment illustrated the burlap is spirally wound upon the supportingelement. Other modes of application may be used.

As is well understood in the art, the purpose of employing two or moresilencing sections having different structural arrangements andtherefore different functional characteristics is to obtain efficientsilencing action over a broad range of pulsation frequencies.

In Fig. 3 a modified form of the invention is combined with a silencingsection similar to that of Fig. 1. This device may be employed as anintake silencer and is intended to be connected to the intake pipe atthe inlet end thereof. Casing I8 and end flanges I9 and 2G form anenclosure which is divided into two sections by a partition flange 2 I.Intake end flange I9 is preferably formed to provide a graduallyconverging passageway for the gases as they enter the silencer. Aperforated tube 22 extends inwardly from this flange toward a centralopening in partition flange 2I, leaving a gap between the end of thetube and the partition for direct communication with the space 23. Afabric layer 24 encircles tube 22.

In the second section of this unit a perforated tube 25 extends from thecentral opening in partition 2I through a similar central opening in endflange 20. A partition 26 divides the space around tube 25 into twoparts. A layer of fabric 2l is placed around one portion of tube 25 anda layer of fabric 28 covers the remaining portion. If desired, two ormore partitions may be used to divide the space around tube 25 intothree or more separate chambers.

As the description and illustrations herein indi cate, the effectiveperformance of the invention is not conditioned upon critical structuralmaterial or dimensions. Any relatively thin pervious brous material, notlimited to the examples herein given, may be used, and directcommunication between the main conducting channel and the expansionspace surrounding it is not necessarily harmful. Although particularmaterials are specified in the descriptions of the devices of Figs. 2and 3, it will be understood that any of the porous fibrous fabrics ormaterials herein claimed as suitable may be used in these embodiments aswell as that of Fig. l. It will be appreciated, however, that theadvantageous effects of the pervious tube segment are increased withincreased effective area of the material.

I claim:

1. A silencer for pulsating gas streams comprising an elongated casingforming a chamber having an inlet opening at one end and an outletopening at the other end thereof and e. conduit having walls comprisinga textile fabric pervious to air and sound extending from said inlet tosaid outlet opening and leaving a substantial space around said conduitwithin said chamber, said conduit forming a dilatable sleeve unconnedexcept adjacent the ends thereof.

2. A silencer in accordance with claim 1 in which the conduit consistsof a knitted sleeve.

3. A silencer in accordance with claim l in which the conduit consistsof bias-cut woven fabric.

4. A silencer for pulsating gas streams comprising an elongated casingforming a chamber having an inlet opening at one end and an outletopening at the other end thereof and a conduit having walls comprising atextile fabric pervious to air and sound extending from said inlet tosaid outlet opening and leaving a substantial space around said conduitwithin said chamber, said conduit forming a dilatable sleeve unconfinedexcept adjacent the ends thereof.

5. A silencer for pulsating gas streams comprising an elongated casingforming a chamber having an inlet opening at one end and an outletopening at the other end thereof and a conduit having walls comprising asingle layer of a textile fabric pervious to air and sound extendingfrom said inlet to said outlet opening and leaving a substantial spacearound said conduit within said chamber, said conduit forming adilatable sleeve unconflned except adjacent the ends thereof.

6. In a silencer for pulsating gas streams, a silencing sectioncomprising means forming a chamber having -an inlet and an outletopening, a perforated tube of self-sustaining material extending betweensaid inlet and outlet openings within said chamber, and a textile fabricpervious to air and sound substantially covering said perforated tube,said fabric forming a dilatable sleeve unconned except adjacent the endsthereof.

'7. In a silencer for pulsating gas streams, a silencing sectioncomprising means forming a chamber having an inlet and an outletopening, a perforated tube of self-sustaining material extending betweensaid inlet and outlet openings within said chamber, and a single layerof a textile fabric pervious to air and sound substantially coveringsaid perforated tube, said fabric forming a dilatable sleeve unconiinedexcept adjacent the ends thereof.

8. In a silencer for pulsating gas streams, a silencing sectioncomprising means forming a chamber having an inlet and an outletopening, a

perforated tube of self-sustaining material extending between said inletand outlet openings Within said chamber, and a strip of textile fabricpervious to air and sound spirally wound around said tube andsubstantially covering the same, said fabric forming a dilatable sleeveunconned except adjacent the ends thereof.

9. In a silencer for pulsating gas streams, a silencing sectioncomprising means forming a chamber having an inlet and an outletopening, a, perforated tube of self sustaining material extending intosaid chamber from said inlet opening toward said outlet opening butterminating short thereof, and a textile fabric pervious to air andsound substantially covering said tube, said fabric forming a, dilatablesleeve unconned eX- cept adjacent the ends thereof.

RALPH L. LEADBETTER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,916,908 Stacey et al July 4,1933 2,043,731 Bourne June 9, 1936 2,089,492 Lambert Aug. 10, 19372,271,892 Bourne Feb. 3, 1942 2,311,676 Maxim Feb. 23, 1943 2,326,612Bourne Aug. 10, 1943

